The syndesmosis is a joint just above the ankle where the tibia and the fibula meet. By definition the syndesmosis is a joint and has characteristics of other joints in the body; however, it does not function like most joints, as there is very little motion between the two bones. Its main functions are, therefore, to provide stability to the ankle joint and allow motion of the joint.
Injuries to the syndesmosis are common and typically relate to an injury involving a twisting or rotation to the ankle, a broken ankle, or even a sprained ankle, resulting in stretched or torn ligaments supporting the syndesmosis.
Certain severe injuries to the syndesmosis require surgical correction to properly align and stabilize the joint so the ligaments can heal in the correct position.
Typically, surgery involves an incision over the outside of the ankle. The fibula (bone) and syndesmosis are identified and exposed. Using direct vision and live X-ray techniques, the syndesmosis, based on learned skill and judgment of the surgeon, is placed into the correct position. The surgeon then “fixes” the syndesmosis in place with an implant. This typically involves one or two screws that go from the fibula bone into the tibia bone. The screws may be placed through a plate that sits on the fibula bone. Alternatively, a suture device may be used instead of screws. A stress X-ray is performed to confirm that the syndesmosis is stable. Stitches are placed to close the incision and the leg is then placed in a splint, cast or boot.
However, syndesmosis surgery is problematic. The medical literature commonly records difficulties with properly reducing and fixating a disruption of the syndesmosis. Improper reduction and fixation of the syndesmosis arises with inaccurate placement of the syndesmosis implant. In cases where an implant is placed too anterior or posterior of the fibula or tibia the fixation device can translate the fibula resulting in malreduction of the tibio-fibular joint.
Further, current techniques in syndesmosis surgery have additional limitations. Surgeons typically drill using solid drills because cannulated screws are ill suited to syndesmosis repair. This restricts the number of attempts a surgeon can make—in contrast with other joint repairs; a surgeon can use a K-wire to visually determine the proper trajectory, remove it and make corrections if needed, and then insert a cannulated screw over the guide wire once it is in the correct position. Therefore, surgeons often have only one attempt to drill and fix the joint. Also, the distance required to drill to depth is relatively large, the typical syndesmosis screw is around 40 mm, thus a small misalignment can result is a clinically significant mal alignment. And, there is no way to use typically available operating room fluoroscopy to ensure that the drill is targeted at the center of the medial tibia. Lastly, even after insertion of the implant, visual inspection of proper fixation is only available using a computed tomography (CT) scan.
Therefore, there remains a need for a method and a device that improves the placement of implants to more accurately and more efficiently repair the syndesmosis.